Techniques for restoring enlarged canals: an evaluation of fracture resistance and bond strength

To verify the influence of fibreglass post diameter, as well as use of accessory posts on fracture resistance and bond strength, when used for restoring enlarged root canals.

One hundred maxillary single-rooted canine human teeth were decoronated and root canals were prepared using a No.4 drill (White Post, FGM, Joinville, SC, Brazil). The roots were assigned to five groups: (EC1) post No.1 (Exacto Cônico, Angelus, Londrina, PR, Brazil); (EC2) post No.2 (Exacto Cônico, Angelus); (EC3) post No.3 (Exacto Cônico, Angelus); (ECA) post No.1 (Exacto Cônico, Angelus) plus two accessory posts (Reforpin, Angelus); (WP) post No.4 (White Post, FGM). Posts 1-4 have a crescent diameter. Posts were luted (Rely X-Arc, 3M ESPE, USA) and composite resin filling cores were prepared for the fracture resistance test (n = 10). For the push-out test (n = 10), roots were sectioned into 1 mm thick slices. Both tests were performed in a universal testing machine. Data were analysed using anova and Tukey's test.

Groups WP and EC3 had higher fracture resistance than the other groups (P < 0.05), which were statistically similar. Root fractures occurred in 14% of the specimens. Groups EC1 and EC2 had lower bond strength values than Groups EC3 and ECA which were lower than the WP Group (P < 0.05). Bond strength was lower in the apical and middle third than in the cervical third of root canals (P < 0.05).

Thicker posts were associated with higher resistance to fracture and bond strength to root canals. Using a post plus two accessory posts improved the bond strength but not the fracture resistance.